Pulverized fuel furnace



Nov. 15, 1932. R. ROOSEN PULVERIZED FUEL FUiNACE Filed Sept. 20, 1930Patented Nov. 15, 1932 UNITED STATES PATENT orrlcs.

RICHARD ROOSEN, OF CASSEL, GERMANY, ASSIGNOR TO STUG KOHLENSTAUBFEUEBUNGPATENTVERWERTUNG G. M. 3. IL, 01 CASSEL, GERMANY PULVERIZED FUEL FURNACEApplication filed September 20, 1930,,Seria1 No. 483,385, and in GermanyOctober 9, 1928.

The invention relates to a method of and means for operating pulverizedfuel furnaces with secondary air of combustion, more particularly withlocomotives.

With furnaces of this class the supply'of secondary air of combustion iswell-known; the usual manner ofsupplying the secondary air however,suffers from several drawbacks. So, despite of a pressure belowatmospheric prevailing in the firebox that would suflice to suck in thesecondary air, incomplete combustion is to be observed, from which factan unsatisfactory supply of the secondary air is to be inferred. Thereason therefor is, that due to wrong guidance of the gases ofcombustion, damming-up of these gases takes place at the very places ofentrance of the secondary air, and thus an unsatisfactory supply of thelatter results. Furthermore, the walls of the firebox and its liner arein jured or entirely destroyed after a short time, because of the factthat due to this Wrong guidance of the fire gases, the hot products ofcombustion immediately strike these walls and liner, as the latter arenot cooled by the secondary air.

Now the invention has for its object to eliminate these drawbacks.Moreover, the method of supplying the secondary air according to theinvention and the means therefor, cause better mixing of pulverized fueland air, and thus a reduction of the time of combustion. Thereforecertain sorts of pulverized fuel can be used which hitherto could not beemployed in pulverized fuel furnaces, such as pulverized pit coal, whichhas the tendency to form coke or the like.

The invention consists in the fact that the secondary air of combustionis supplied to the combustible mixture of air and pulverized fuel in aquantity adequate to the required quantity of this mixture, andsubdivided in such a manner that a separate partial currentof secondaryair is supplied at the following places of the path of the flame: at thezone of distillation of the pulverized fuel, in the range of the firstcombustion of the fuel after distillation, in the range of the maincombustion, in the range of the final combustion, and in the coolingzone of the residues of combustion.

The invention further provides means for carrying out with particularadvantage the indicated method of supplying the secondary air ofcombustion.

In order that the invention can be more readily understood, somepreferred embodiments of the same are diagrammatically illustrated byway of example in the accompanying drawing in which Figure 1 is acentral longitudinal section through the rear portion ofa pulverizedfuelfired locomotive designed according to the invention, I

Figure 2 is a fragmentar similar section showing a modification of t esecondary air 811M215, Figure 3 1s a cross section through a modlfiedfirebox, seen toward the fire bridge, and Figure 4 is a sectionsimilarto Figure 3 showing another modification.

Referring first to Figure 1 of the drawing, 2 denotes the firebox of thelocomotive boiler 3 in the lower portion 1 of which, where otherwise isarranged the ash pan, is disposed above the pulverized fuel burner'orburners 4 a short bridge 5 containing a secondary air passage 6 openinginto the combustion chamber. In the bottom 7 of the firebox 2 are provided further secondary air feeding passages 8, 9, 10 which open into thefirebox in parallel or approximately in parallel to the way A of thecombustion flame, indicated by a dot and dash line. The path of thesecondary air supplied is marked in all figures by full arrow lines. Theair passages 8, 9, 10 on their outer end are in communication with acommon chamber 11 to which the secondary air is supplied in a quantitythat can be regulated by a damper 12. To prevent choking, a protectiveprojection 13 is provided above each of the passages 8, 9, 10. On thelowermost place of bottom 7 is arranged anash an 14 from which theresidues of combustlon collecting therein can be removed by opening adamper 15. Between the wall 16 bounding the firebox on the front end,andthe ash pan 14 there is provided a further secondary air passage 17which extends into the firebox in an inclined upward direction.

In front of the front wall 16 of the firebox is disposed a furthersecondary air passage 18 extending in upward direction, the inlet ofwhich passage opens into the free air and can be regulated by a damper19. A portion of the secondary air supplied through pas sage 18 entersthe firebox 2 through a passage 20 which is formed between an auxiliarystub fire bridge 22 and the main fire bridge 21. The remaining portionof the secondary air supplied through passage 18 is added to the currentof the combustion gases through a passage provided in the fire bridge 21itself and leaves it on its front edge at .23. In order to have the airmore uniformly distributed on these two passages a baflle plate 24 maybe arranged or the two passages may be completely separated from oneanother if required. To obtain-a satisfactory flow of the fire gases,the auxiliary bridge 22 is suitably rounded-ofl' on its underside at 25.If required, branch passages 26 may be provided that lead from thepassage in the bridge 21 to the underside of the latter. The openings20, 23 and 26 may extend either on the entire width of the combustionchamber or may be subdivided as illustrated in Figures 3 and 4. In thisconnection it is of advantage for instance to achieve a subdivided a1rsupply through the main fire bridge 21 by means of pipes embeddedtherein which at the same time impart to the bridge a greater strength.

-Finally, small passages 30 provided in the base of bridge 21 andcommunicating with passage 18 serve to supply secondary air in Ehevicinity of the tube wall 29 of the fireox. Y

In the embodiment illustrated in Figures 2 and 4 the air passage 18merely opens into the space existing between the auxiliary bridge 22 andmain bridge 21, the portion of the air escaping through the upperpassage 27 that undividedly extends on the entire width of the bridge,serving to cool the main bridge 21 while the air escaping through thelower individual openings 28 forms the proper air of combustion for theflame. To increase the effect, the openings 27 and 28 as well as allother air outlets may be designed as nozzles.

The described appliances operate as follows and have the followingeffect.

The flame passes through the firebox on the S-shaped way marked by a dotand dash line A and comes into contact first with the secondary airentering through the passages 6 and 8 in the zone of distillation of thepulverized fuel. Further secondary air is then supplied in the range ofthe primary combustion through the passages 9 and 10 so that at once abrisk combustion takes place. The secondary air further supplied through17 and that added through 20 and 27, 28, and 26 improvethe combustion inthe zone of main combustion. This comparatively cool air at the sametime protects the fire bridge and the lining as itprevents the bricksfrom directly being struck by the flame. Owing to the secondary air thatenters through passages 28, Figures 3 a11d 4, being subdivided intoseveral jets, the current of the combustion gas is loosened so that thesurface of reaction is increased and a quick combustion obtained. Thesecondary air entering through 23 meets the gas current in the range ofthe last stage of combustion, while secondary air in the 'cooling zoneof theresidues of combustion,

that is close to the tube wall 29 of the firebox, is supplied throughthe passages 30. It may still be noted that the secondary air currententering through passage 6 besides adding air in the zone ofdistillation still has the effect of urging the flame down below thefire bridge so that it comes into intimate contact with the secondaryair entering there. A satisfactory guidance of the flame without shocksis obtained both by the respective faces of the combustion chamber beingrounded off at the places of deflection, such as 25, and by thesecondary air being supplied in currents which as far as possible extendin parallel to the gas flame everywhere they enter the firebox. so thatno damming is caused anywhere by the fire gases and the supply of thesecondary air is not impeded. This causes in turn, a quick combustionwhich is of great importance with regard to the comparatively smallcombustion chambers of locomotives.

Without deviating from the essence of the invention the individualelements thereof may be combined with one another as desired thermore,the number and situation of the secondary air supply passages may bevaried according to the 'fuel employed'and to the length of the path atdisposal for the flame. Finally, the passages'8, 9, 10 may open into theriser of every step of a stepped bottom of the firebox, whereby chokingof these openings is prevented still in a higher degree.

What I claim is:

- 1. A pulverized fuel furnace having a firebox. a fire bridgetherein,apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said firebox atleast approximately in parallel with the entrance path of the fuel, anauxiliary fire bridge spacedly arranged below said fire bridge, andanother secondary air supply passage opening into the space existingbetween said fire bridge and auxiliary fire bridge.

2. A pulverized fuel furnace having a firebox, a fire bridge therein, apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said firebox atleast approximately in parallel withthe entrance path of the fuel, anauxiliary fire bridge spacedly arranged below said fire bridge, andanother secondary air supply passage open ing into the space existingbetween said fire bridge and auxiliary fire bridge, the latter beingrounded off on its edge facing said burner.

3. A pulverized fuel furnace having a firebox, a fire bridge therein, apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said firebox atleast approximately in parallel with the entrance path of the fuel, anauxiliary fire bridge spacedly arranged below said fire bridge, asecondary air supply passage opening into the space existing betweensaid two fire bridges, and another secondary'air supply passage throughsaid auxiliary fire bridge.

4. A pulverized fuel furnace having a firebox, a fire bridge therein, apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said firebox atleast approximately in parallel with the entrance path of the fuel, anauxiliary fire bridge spacedly arranged below said fire bridge, asecondary air supply passage opening into the space existing betweensaid two fire bridges, and a subdivided secondary air supply passagethrough said auxiliary fire bridge.

5. A pulverized fuel furnace having a firebox, a fire bridge therein, apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said firebox atleast approximately in parallel with the entrance path of the fuel,other secondary air supply passages arranged in said fire bridge andopening into the front edge of the latter, passages branching off fromsaid fire bridge passagesand opening at the underside of said firebridge, and an upwardly directed secondary air supply passage in saidfire bridge in its base.

6. A pulverized fuel furnace having a fire box, a fire bridge therein, apowdered fuel burner mounted to direct fuel towards said fire bridge,secondary air supply assages arranged in the bottom of said fire ox atleast approximately in parallel with the entrance path of the fuel, anauxiliary fire bridge spacedly arranged below said fire bridge, anothersecondary air supply passage opening into the space existing betweensaid fire bridge and auxiliary fire bridge, and subdivided into severalindividual passages.

7. A pulverized fuel furnace having a firebox, a fire bridge therein, apowdered fuel burner mounted todirect fuel towards said fire bridge,secondary air supply passages arranged in the bottom of said fire box atleast for protecting said first mentioned passages from being choked bythe residues of the combustion. I

The foregoing specification signed at Frankfort-on-the-Rhine, Germany,this 4th day of September, 1930.

- RICHARD ROOSEN.

